Electrical information storage means



May 24, 1955 F. c. WILLIAMS ET AL 2,709,239

ELECTRICAL INFORMATION STORAGE MEANS Original Filed June 2, 1950 3Sheets-Sheet 1 PULSE GE NR.

00 T GEN/e. TROBE Y SCAN as ms 28 23 INVENTORS FREDER/c a W/LL/AMS, TOMK/LBUR/V, GEOFFREV a TOUT/LL ma m Mg %m ay 24, 1955 w uA g AL 2,709,239

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GEOFFREY c. roar/1.1.

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ATTORNEYS May 24, 1955 F. c. WILLIAMS ET AL 2,709,230

ELECTRICAL INFORMATION STORAGE MEANS Original Filed June 2 1950 3Shets-Sheet 3 mpur FROM AMPLIFIER I S 33 MA 33 0 ourur 70 CRT 0/6 GRID"EASE 04s 450v H par READ WR/TE INVENTORS FREDERIC a WILLIAMS, 70MK/LBURN, GEOFFRE Y c. mar/1.1.

ATTORNEYS ELECTRICAL iNFonMATroN STORAGE r/mANs Frederic CallandWilliams, Homily, Tom Kiiburn, Davyhulme, and Geoffrey Colin Tootiil,Swindou, England, assignors to National Research DevelopmentCorporation, London, England, a corporation of Great BritainContinuation of application Serial No. 165,622, June 2, 1950. Thisapplication May 8, 1953, Serial No. 353,319

Claims priority, application Great Britain June 7, 1949 12 Claims. (til.315--22) The present invention relates to electrical information storagedevices of the type in which an insulator is scanned by an electron beamto set up electric charges representing the information to be stored.Such a device is described for example in United States patentspecification Serial No. 790,879, filed December 10, 1947.

The present application is a continuation of our eo-pending applicationSerial No. 165,622, filed Tune 2, 1950, for Electrical InformationStorage Means.

Such storage devices are used in binary digital computing machines inwhich there is stored on one or more lines of the insulating surface aword that is to say a number of digits representing, according to thebinary system of notation, a numerical quantity or representing aninstruction. Three methods of storing such words are describedrespectively in the above-numbered specification and in thespecifications of co-pendiug patent applications Serial No. 50,136,filed September 20, 1948; 124,192, filed October 28, 1949, and 124,577,filed October 31, 1949, and are discussed together in a paper by F. C.Williams and T. Kilburn entitled A storage system for use with binarydigitai computing machines, published in Proceedings of the Institutionof Electrical Engineers, vol. 96, part 111, No. 40, page 81, March 1949.The method which has hitherto been most used is the one described in thespecification of application Serial No. 50,136, filed September 20,1948, and referred to in the paper as dot-dash. In this dot-dash systeminformation of one kind (e. g. the binary digit O) is stored byintensifying the beam while it is stationary or is sweeping over a shortlength of line and information of a second kind (e. g. the binary digit"1) is stored by intensifying the beam when it is sweeping over a longerlength of line.

The two states of charge corresponding to the digits and 1 areregenerated by using the initial transient generated in a pick-up platecapacitively coupled to the surface of the insulator bearingthe charges,since a dot gives rise to a negative-going initial transient and a dashto a positive-going initial transient when the charged areas areilluminated (that is irradiated) by the beam. The initial transient can,therefore, be applied to control the beam intensity in such a way that adash is written when the initial transient is positive and a dot whenthe transient is negative.

Now in devices of this kind it has been found that there is a minimumspacing which can be used between the lines because the fllurnination ofan area can lead to disturbance of the charges stored in areas inneighbouring lines. This elfect is called action line limitation and isdiscussed in the paper referred to above.

The effect is not so great in the direction of the line for two reasons.Firstly because any spread due to illumination of the tail of a dash isslight and is quickly corrected when the next dot (or the first part orhead of the next dash) is illuminated and secondly because the spreadproduced by a dot on the tail of the previous dash is not so seriousbecause the tail of the dash has only a m amazes Patented May 2 1955small effect on the production of the regenerating transient, if thescanning beam is caused to pause while illuminating a dot and the headof a dash. Accordingly the spacing in the line can be closer than thespacing between the lines.

An object of this invention is to provide means for storing informationwhereby a greater number of digits can be stored on a given length ofline and hence on a given area of insulating surface than in thepreviously proposed means.

According to this invention in an information storage device of the typedescribed information of one kind is stored by intensifying the electronbeam when it is stationary or is sweeping over a length of line andinformation of a second kind is stored by applying the electrical outputfrom time-base circuit to beam deflection means to deflect the beam in adirection at an angle to said line either when the beam is stationary oris sweeping over a length of line.

The invention will be better understood by reference to the accompanyingdrawings in which Figure l is a block-schematic diagram of storage meansaccording to this invention, Figure 2 shows waveforms illustrating theoperation of the storage means shown in Figure 1, and Figure 3 is acircuit diagram of the gate circuit of Figure 1.

Referring first to Figure 1 there is shown a cathode ray tube 11employed as a digit store. The tube comprises a cathode 12, a controlgrid 13, a first anode 14, a second anode 1S and a third anode 16constituted by a conducting surface on the wall of the tube adjacent tothe screen S of the tube and X and Y deflecting plates 17 and 18respectively. The second and third anodes 15 and 16 are held at earthpotential and the remaining electrodes have suitable negative potentialsapplied to them to cause the beam to operate at a beam velocity suchthat when a spot on the screen is bombarded with electrons the number ofsecondary electrons initially emitted from the spot exceeds the numberof primary electrons which arrive. A signal pick-up electrode 19 is heldsecurely on the outside wall of the tube adjacent to the screen. Numbersin binary form are stored as charge patterns on a number of parallellines on the cathode ray tube screen, the digit 0" being stored bycausing electrons to fall on an area shown in Figure 2(a) and the digit1 being stored by causing electrons to fall on an area shown in Figure2(b).

A pulse generator 21 produces regularly recurring pulses which are usedto synchronise the operation of all the correlated parts of theapparatus. These pulses are fed to a divider circuit 21 which countsdown to provide synchronising pulses for the X time-base generator 22and the Y time-base generator 23 which provide deflection voltages whichare applied to the X and Y deflector plates to set up a raster of anumber of horizontal lines; between lines the electron beam of thecathode ray tube is blacked out. The particular form of Y scan employedis described in detail in the specification of U. S. patent applicationSer. No. 93,612, filed May 16, 1949. Briefly it causes the lines to beexplored sequentially but alternately with any selected line. Thus ifline it) is selected the scanning, beginning with line 1 proceeds 1, 1t2, 1i 3, 10, etc. This form of Y scan, therefore, enables theinformation on any selected line to be read without the need to waituntil this line reached in the normal sequential scanning process. Eachline is divided into a number of elements and during the scan of a lineeach element is normally illuminated by applying a dot pulse shown inFigure 2(a) from a dot pulse generator 24 through a gate circuit 25 tothe cathode ray tube grid. The dot pulse generator is synchronised bythe pulse generator 20. However, an element can also be illuminated byapplying to the cathode ray tube grid through the gate circuit 25, a

dash pulse shown in Figure 2((1) obtained from a dash pulse generator26. The dash pulse generator is also synchronised by the pulse generator26.

The waveform of the voltage output of the X scan generator 22 is shownin Figure 2(a) and as can be seen it contains steps of constant voltagewhereby the beam is caused to pause for the duration of each dash pulse.Output pulses from the pulse generator are also applied to a further Ytime-base circuit 31 which produces a time base voltage shown in Figure2( having a working stroke extending over the duration of a dash pulseand a fly-back stroke between the working strokes.

When the digit 0 is to be recorded on an element the electron beam ofthe cathode ray tube is switched on by applying a dot pulse to thecathode ray tube control grid. Simultaneously the electron beam isdeflected a little in the Y direction by the initial portion of the scanperiod of the time-base voltage shown in Figure 2(f). Electrons,therefore, reach an area represented in Figure 2(a). In Figures 2(a) and2(b) the direction of scanning is indicated by an arrow A. When thedigit 1 is to be recorded the electron beam of the cathode ray tube isswitched on by applying a dash pulse shown in Figure 2(d) to the cathoderay tube grid. Whilst the beam is thus switched on it is deflected byone whole working stroke of the time-base voltage shown in Figure 2(f),the electrons therefore reaching an area shown in Figure 2(b).

Although the direction of the deflection produced by the time-base 31 ispreferably at right angles to the line of scan, it may be at an acuteangle thereto.

In an alternative rraangement the initial part of the waveform at Figure2(f) may be level, that is to say the beam may be held stationary duringthe dot period so that the dot produced is not slightly elongated.

It may be noted here that the spacial length of the dash may easily beadjusted by adjusting the slope of the waveform at Figure 2(f). This ismore convenient than in the previous dot-dash system in which thespacial length of a dash was dependent upon the timing of the variouspulses and the velocity of scanning and was not readily adjustable.

When an element is illuminated during a scan, a transient pulse signalis generated in the pick-up electrode 19 having a sign dependent onwhether a charge due to a stored 0 digit was previously recorded orWhether a charge due to a stored 1 digit was previously recorded. If acharge due to a 0 digit was recorded a negative signal as shown inFigure 2(g) will be generated and if charge due to a 1 digit wasrecorded a positive signal as shown in Figure 2(h) will be generated.The reason for this will be made clear by a perusal of theaforementioned paper.

The transient signals are used to regenerate the stored information in amanner now to be explained. Signals from the pick-up electrode 19 areamplified in an amplifier 27 and fed to the gate circuit 25. The gatecircuit is also fed with strobe pulses, shown in Figure 2(i) obtainedfrom a strobe pulse generator 28 and synchro nised by the dot pulsegenerator 24. If a positive transient pulse signal, obtained byilluminating the beginning of a charged area of dash shape on thecathode ray tube screen corresponding to a stored 1 digit, is fed to thegate circuit 25, the gate circuit operates to cause a dash area to beregenerated on the screen by applying a dash pulse from the dash pulsegenerator 26 to the cathode ray tube grid, otherwise a dot pulse fromthe dot pulse generator 24 will be applied to the cathode ray tube gridand a dot area will be recorded.

New information can be written on the cathode ray tube screen byapplying signals to the gate circuit 25 via terminal 29. Output signalsfor a further part of the computor consisting of a dash pulse for eachstored 1 digit may be read out from the gate circuit 25 via terminal 30.

The gate circuit 25 may have the form shown in Figure 3. in this figure,dot pulses, which are negativegoing from a rest level of +5 volts, fromthe generator 24 of Figure 1 are applied through a diode D16 to thecontrol grid of a valve V13. During each pulse the anode current in thisvalve is cut ofr" and its voltage rises until caught by a diode D17 at+50 volts. The resulting Voltage pulse is fed to the control grid of acathode-follower V1 and the output voltage across the cathode loadresistance of this valve is taken from terminal 32 to the control grid13 of the cathode ray tube 11 of Figure 1. In this way dots are producedon the screen of the tube.

if a positive initial transient appears at the output of amplifier 27(Figure l) owing to the illumination of a dash area on the screen of thetube 11, this transient appears at terminal 33 of Figure 3 and isapplied biased to l5 volts to the control grid of a valve V11. Strobepulses positive-going from a resting level of -10 volts, are also fedthrough a diode D11 to the control grid. The anode current of valve V11is normally cut off and is switched on only when a positive pulse fromthe amplifier appears on the grid of V11 simultaneously with a positivestrobe pulse. The negative pulse produced at the anode of V11 when theanode current of this valve is switched off is applied to the grid of acathode-follower valve V12 which has the upper limit of its control gridvoltage defined at zero volts by diodes D14 and D13 and its lower limitdefined at l5 volts by a diode D15 through which negative-going dashpulses are applied from a rest level of +5 volts to the control grid ofV12. A condenser C11 prevents the voltage on the control grid of V12from changing unless the grid is driven. In the presence of a dashpulse, therefore, the grid of valve V12 is driven negative by the pulsefrom the anode of the valve V11 and will remain at about l5 volts forapproximately the period of the dash applied through D15. It will thenbe driven to zero volts and will remain at this level until anotherpositive pulse is applied to V11.

The effect of the dash pulse applied to the grid of V13 is to maintainthis valve, which has already been cut off by a dot pulse, cut off forthe period of a dash. In this way a dash area of charge is regeneratedon the screen of the cathode ray tube. If no positive transient isapplied to V11 this indicates that a dot area of charge has been scannedand the effect is that the valve V12 remains cut off and a dot area ofcharge is regenerated.

While there have been described what are at present considered to be thepreferred embodiments of this invention it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,intended in the appended claims to cover by generic terms all suchchanges and modifications as fall within the true spirit and scope ofthe invention.

We claim:

1. An information storage device comprising a cathode ray tube, anelectric charge retaining surface, means for sweeping the electron beamof the tube along a line over the charge retaining surface, means forintensifying the beam to produce on the said surface a first state ofcharge representative of one item of information, and means fordeflecting the beam in a direction inclined with respect to said line,whilst the beam is intensified, in order to produce on the said surfacea second state of charge representative of another item of information.

2. A device according to claim 1, wherein said direction issubstantially at right angles to said line.

3. An information storage device comprising a cathode ray tube, anelectric charge retaining surface, means for sweeping the electron beamof the tube along a line over the charge retaining surface, a firstgenerator of recurrent pulses, means to apply pulses from said generatorto intensity the cathode ray beam, deflecting means for defleeting thebeam in a direction inclined with respect to said line, a source ofrecurrent deflecting voltages, said deflecting voltages being phased tooccur at least partly after each of said pulses, means to apply saidvoltages to said deflecting means, a second generator for generatingpulses phased to occur at least partly after each of the first-namedpulses, and means for selectively applying pulses from said secondgenerator to maintain intensification ofsaid beam after the cessation ofeach of the firstnamed pulses.

4. An information storage device comprising a cathode ray tube, anelectric charge retaining surface, a generator of a stepped saw-toothtime-base voltage, the waveform of said voltage comprising periods ofchanging voltage separated by periods or" constant voltage, means forapplying said voltage to deflect the beam of said tube along a line,pauses in the movement of the beam occurring during said periods ofconstant voltage, means for intensifying the beam during a part of eachof said pauses, means for deflecting the beam in a direction inclinedwith respect to said line during at least part of each of said pauses,and selectively operable means for extending the periods ofintensification of the beam over at least the greater part of saidpauses.

5. An information storage device comprising a cathode ray tube, aninsulator disposed within the evacuated envelope of said tube, means forsweeping the electron beam of the tube along a line over the insulator,a first generator of recurrent pulses, means to apply pulses from saidgenerator to intensify the cathode ray beam and generate a charge onsaid insulator, deflecting means for deflecting the beam in a directioninclined with respect to said line, a source of recurrent deflectingvoltages, said deflecting voltages being phased to occur at least partlyafter each of said pulses, means to apply said voltages to saiddeflecting means, a second generator for generating pulses phased tooccur at least partly after each of the first-named pulses, a pick-upplate for receiving signal voltages corresponding to changes in saidcharge on said insulator and means for applying said signal voltages tocontrol the application of pulses from said second generator to prolongthe intensification of the cathode ray beam.

6. A method of storing information in the form of electric charges on aninsulator comprising the steps of sweeping an electron beam along a lineover the insulator, intensifying the beam to produce on the insulator afirst state of charge representative of one item of information,deflecting the beam in a direction inclined to said line at an angle offrom thirty to ninety degrees during the intensification of said beam toproduce on the insulator a second state of charge representative ofanother item of information, picking up transient pulse signals fromcharges on the insulator and controlling the intensity of said beam bythe transient pulse signals in order to regenerate said charges.

7. An information storage device comprising a cathode ray tube, aninsulator, pickup means associated with said insulator for receivingvoltages corresponding to changes in charge of said insulator, means forsweeping the electron beam of the tube along a line over the insulator,means for deflecting the beam in a direction inclined with respect tosaid line, a gating circuit connected to the control grid of saidcathode ray tube, amplifier means connecting said pickup means and saidgating means, pulse generating means connected to said deflecting meansand said gating circuit, said gating circuit having information inputand output terminals, whereby the beam may be intensified to produce onthe insulator a first state of charge representative of one item ofinformation and deflected during the period of intensification toproduce on the insulator a second state of charge representative ofanother item of information with high space efficiency and such statesof charge may be regenerated to maintain them for a desired period, maybe read and may be changed by rewriting as desired.

8. The combination set forth in claim 7, said gate circuit comprising agrid controlled tube connected to said amplifier and having its gridconnected to a source of pulses, a cathode follower tube connected tothe plate of said grid controlled tube through voltage limiting means,stabilizing condenser means connected to the control grid of saidcathode follower tube, a grid controlled tube having its grid connectedto the cathode of said cathode follower and a second cathode followertube having its control grid connected to the plate of said last namedtube, the output of said second cathode follower being connected to thecontrol grid of said cathode ray tube.

9. In combination an information storage device comprising a cathode raytube, an electric charge-retaining surface, means for sweeping theelectron beam of the tube along a line over said electriccharge-retaining surface, first control means controlling the beam toproduce on the charge-retaining surface a first state of chargerepresentative of one item of information, and second control means fordeflecting the beam in a direction inclined with respect to said line inorder to produce on the charge-retaining surface a second state ofcharge representative of another item of information.

10. The combination set forth in claim 9 in which said first controlmeans comprises means for switching off the beam during scanning.

11. The combination set forth in claim 1, and means for switching offthe beam during scanning.

12. The combination as set forth in claim 9 comprising a pick-up platecapacitively coupled to said chargeretaining surface and means to applyvoltages generated in said plate when charged areas of said surface arebombarded by said beam to control said beam in order to regenerate thecharges on said areas.

References Cited in the file of this patent UNITED STATES PATENTS2,034,704 Nakashima et al Mar. 24, 1936 2,434,264 Edson Jan. 13, 19482,439,321 Starr Apr. 6, 1948 2,440,301 Sharpe Apr. 27, 1948 2,451,005Weimer et al. Oct. 12, 1948 2,454,410 Snyder, Jr. Nov. 23, 1948

